In general, mobile devices, such as smartphones and the like, play back one of contents, such as videos and the like, at a time due to limited performance. However, the recent change in decoding of contents such as videos not only from software but also from hardware allows a plurality of contents to be played back at a time in mobile devices.
However, a user interface for playback of the plurality of contents is unavailable, which makes it difficult to playback the plurality of contents in a mobile device at a time.